The present teachings relate to detector arrays with electronically adjustable detector positions and methods for application of the detector arrays with electronically adjustable detector positions. The applications include compensating for misalignment in an image scanner, and synthetic improvement of image resolution.
There are a number of possible applications for detector arrays, which receive electromagnetic radiation from a target object, where adjustable detector positions would be desirable. One of those applications is compensation for misalignment in image scanners. Another application is the synthetic improvement of spatial resolution.
A time delay and integration (TDI) image scanner accumulates multiple exposures of the same object as the object moves relative to the scanner. When a scanning imager, or elements therein, sweep through a scan that is off-nadir the image tracks across the focal plane in an arc and image elements that begin in one scan column may end in a different scan column. If uncorrected, this smears the image across multiple columns and degrades modulation transfer function (MTF). Digital corrections can account for the approximate column location of each image element, as an integer, through the course of a scan, reducing smear to a half-pixel, but cannot compensate for the splitting of image elements across two detector pixels as they track from one column into the next.
“Off-nadir” scan smearing can be corrected by accounting for the tracking of the image across columns of a multi-row scanner during a scan. This can be done digitally; for instance, in the case of time-delayed integration (TDI) scanners, one might add rows 1-10 of column 1 to a single integrated image pixel, followed by rows 11-20 of column 2. This approach can reduce smear to a half-pixel. Correction can also be done by dynamic aggregation of detector pixels of a smaller size than corresponding to the final image pixel (in the cross-scan dimension) into single image pixels. This approach, again, can reduce smear to, at best, a half-pixel. Since for both these cases, the amount of smear is relative to the detector pixel size, it can be reduced by reducing the cross scan pixel dimension. However, this requires additional pixel unit cells. For hybrid sensors, the number, size, and density of detector-to-readout integrated circuit (ROIC) interconnects therefore present additional constraints in terms of spacing and alignment tolerances. The addition of pixel unit cells is also not always desirable since it requires compression of more per-pixel circuitry into the same space for a given detector size, and it can increase the overall noise of the signal collected by the detector by reason of multiplying constant per-pixel noise sources.
Similar needs for correction arise from other factors that can displace an image from the nominal column in which it would normally be expected, including but not limited to: mechanical jitter; optical aberration in the system; optical aberration caused by environments interposed between the target object and the imaging system.
There is a need for systems and methods that can reduce misalignment or smear to better than half a pixel.
There is a need in a number of applications, such as, but not limited to, improving image resolution, for a system and method for adjusting detector position and size.